Bots seem to have positive ROI, but most of the time at the last minute they get new bids and they turn negative. You can check the bots and see how often they go to -10%. Some bots have no downside limit, if they receive a lot of bids the ROI could be very negative. I already use the resteem services too, all of them. That's an extra charge too. The money made by the "attention" is close to zero, whales are delegating their SP to the bots.